Method of increasing engine thrust



United States Patent 2,901,886 METHOD or INCREASING ENGINE THRUST MonaPhyllis Doemer, Walnut Creek, Calif., assignor to The Dow ChemicalCompany, Midland, Mich., a corporation of Delaware,

No Drawing. Application-March 21, 1956 Serial'No. 572,805

an engine an improved high energy fuel.

.Several materials have been usedin the pastas high energy fuels forrocket and jet engines. The term high energy fuel refers to fuels whichspontaneously ignite and violently burn when mixed with an oxidizingagent such as hydrogen peroxide, nitric acid or nitrogen tetroxide toproduce thrust in a rocket, jet or turbo-jet engine. High energy fuelsfrequently used in such engines include hydrazine, hydrazine hydrate,aniline and aliphatic hydrocarbons. A particular disadvantage of suchfuels has been their liquidus properties whereby they freeze attemperatures commonly encountered in missile and jet plane flight.Another disadvantage of many such fuels has been their inability toproduce high thrusts due to their unfavorable heats of combustion orundesirable ignition characteristics. A fuel which would be charaoterized by a high heat of combustion, low freezing point, short ignitiondelay and high specific impulse would be of outstanding value in thedevelopment of rockets and missiles. It is thus clearly evident thatfuels having improved ignition, combustion and liquidus properties wouldbe a distinct advantage to the development of the rocket and jet engineindustry.

One object of this invention is to provide a novel method of obtainingthrust from an engine capable of burning a high energy fuel. Anotherobject is to provide an improved method of increasing the thrust of anengine which burns a high energy fuel by supplying to the combustionzone of such an engine a fuel having very desirable liquidus, ignitionand combustion properties. Other objects will appear throughout thefollowing description and appended claims.

This new and improved method of providing thrust to an engine which willburn a high energy fuel will be more fully described hereinafter and thenovelty thereof will be particularly pointed out and distinctly claimed.

In accordance with the present invention, it has been discovered thatthrust may be obtained from an engine capable of burning a high energyfuel by supplying to the combustion zone of such an engine a propynylcompound having the general formula:

HCEC-CHr-IiF-R where R is hydrogen, methyl, ethyl or Z-propynyl and R isamino, methyl or allyl, along with an oxidizer such as nitric acid,nitrogen tetroxide, hydrogen peroxide or oxygen. These propynylcompounds have very desirable overall characteristics such as high heatof combustion, high specific impulse, wide liquidus range and 2 a shortignition delay whereby theyare particularly adapted to be employed ashigh energy fuels. The compounds are stable liquids in air at normaltemperatures and pressures. (2-propynyl) hydrazine andl,1-bis(2-propynyl=)' hydrazine freeze at approximately 60 C. and '-4S C;

and boil at 63 66 C. at 17 millimeters pressure and 6l63 C. at 4millimeters pressure, respectively. Dimethyl (Z-propynyl) amine andallyl di(Z-propyhyl) amine freeze at approximately .44 C. and -60 C.respectively. The compounds also possess much higher heats of combustionthan hydrazine as shown in the table below in which the heat ofcombustion is expressed in kilocalories per pound:

Heat of Compound: combustion Hydrazine v V 1930 (Z-propynyl) hydrazine3540 1,1-bis (Z-propynyl) hydrazine 4020 l-methyl-l-(Z-propynyl)hydrazine 3780 1-ethyl-l-(2-propynyl) hydrazine; 3930 Methyldi(2-propynyl)- amine 4440 Dimethyl (Z-propynyl) amine 4330 Allyldi(Z-propynyl) amine 4480 When operating in accordance with the presentinvention, the propynyl compound and the oxidizing agent are separatelymetered into the combustion chamber of the engine where combustion andviolent burning take place spontaneously. In such operations, it isdesirable that the oxidizing agent be introduced into the combustionchamber at a rate and in an amount suificient to efiect substantiallycomplete combustion of the propynyl fuel compound. The rate at whichthrust is developed in the engine varies directly with the rate at whichthe propynyl compound and oxidizing agent are metered into thecombustion chamber. The propynyl compound may be supplied to thecombustion zone along with other additives such as aniline, substitutedanilines or aliphatic hydrocarbons. The thrust developed from thecombustion of the fuel is found to be considerably greater when one ormore of the propynyl hydrazines or propynyl amines is used as the fuelthan when hydrazine is used. Since the thrust developed in an engine isdirectly proportional to the heat of combustion of the fuel employed, itis evident that an engine burning a propynyl hydrazine or propynyl aminecan propel a missile proportionately further or can propel aproportionately greater load than an engine burning a conventional fuel.

The propynyl hydrazine and propynyl amine compounds used as fuels in themethod of the present invention to increase engine thrust may beprepared by reacting propargyl bromide or propargyl chloride withhydrazine, methyl hydrazine, ethyl hydrazine, methylamine or allylamine.The reaction is carried out in an inert organic solvent such as a loweralcohol or diethyl ether. The reaction is exothermic and takes placesmoothly at l0 to C. with the production of the desired product and thehydrohalide of the hydrazine or amine reagent. Good results are obtainedwhen employing one molecular proportion of propargyl halide with atleast two molecular proportions of the hydrazine or amine reagent. Uponcompletion of the reaction, the desired product may be separated byfractional distillation under reduced pressure.

In accordance with the patent statutes, this invention has been fullyand completely described including what is now considered to be one ofits best embodiments. However, it will be apparent to those skilled inthe art that other variations are possible. Thus, it should beunderstood that within the scope of the appended claims this inventionmay be practiced otherwise than as specifically described.

WhatI claim is: 1. In a method of obtaining thrust from an engineadapted for producing thrustupon combustion therein of; a high; energy,fuehwith; an, ;-oxidizer-. which-- -will-: efiecta" hypengolieandspontaneous; cQmbIQSt -OII with th fu l, and;Wl1erein-the;fueL and anamount Ofgllhe oxidizer suflii-xcienL toflefifect substantially:complete combustion ,thereof,

are simultaneously supplied, to:- the com ustion: zone of said; enginethesimprovement which comprisesemployingz as'the highsenergyfueLa-membenofigthe group-iconsisting of; (2 -prOPY-. lYL) hydrazine,1';1-bis(2-pr opyny1) hydrazine, 1 -methy1-1I-( 2 propyny1): hydrazine,-1-ethyl-1-(;2-:

4 pound suppliedrtothe. com-bustionzonev is. di.u1ethyl )(2- propynyl)amine.

6. A method according to -claim 1 in which the compound supplied to thecombustion zone is allyl di(2- propynyl) amine.

7. A method of increiiinglizthe thrust of an engine capab1e,. of,burning afihigh energy ,fuel which comprises sutlicirelwto.effecu-substantiaily completes; combustion of the fuel, the high energyfuel bei'ngseleeted' from the group consisting of,.(2-rppynyl),;hydrazine,; 1,lbis (2- propynyl) hydrazinemthifl vlqz-pubiiynyl) hydrazine, l-ethyl-l-(Z-propynyl) hydrazine, methyldi(2-propynyl) amine, dimethy1 (2-propynyl) aniine -and allyldi(2-propynyl) amine, and the oxidizer being selected from the groupconsisting of nitric acid, nitrogen tetroxide, hydrogem-peroxide andoxygenk a ReferencesaGitediinl theifile" of. this patent: NIIEDLPSTATBsPATENTS"

1. IN A METHOD OF OBTAINING THRUST FROM AN ENGINE ADAPTED FOR PRODUCINGTHRUST UPON COMBUSTION THEREIN OF A HIGH ENERGYH FUEL WITH AN OXIDEZERWHICH WILL EFFECT A HYPERGOLIC AND SPONTANEOUS COMBUSTION WITH THE FUEL,AND WHEREIN THE FUEL AND AN AMOUNT OF THE OXIDIZER SUFFICIENT OT EFFECTSUBSTANTIALLY COMPLETE COMBUSTION THEREOF ARE SIMULTANEOUSLY SUPPLIED TOTHE COMBUSTION ZONE OF SAID ENGINE, THE IMPORVEMENT WHICH COMPRISESEMPLOYING AS THE HIGH ENERGY FUEL A MEMBER OF THE GROUP CONSISTING OF(2-PROPYNYL) HYDRAZINE, 1,1-BIS(2-PROPYNYL) HYDRAZINE,1-METHYL-I-(2-PROPYNYL) HYDRAZINE, 1-ETHYL-I-(-PROPYNYL) HYDRAZINE,METHYL DI(2-PROPYNLY)AMINE, DIMETHYL(2-PROPYNL)AMINE AND ALLYLDI(2-PROPYNYL)AMINE.